Blocks Stability in Plunge Pools under Turbulent Rectangular Jets

Energy dissipation through a rectangular jet discharging into a plunge pool is a common approach in dams engineering. This paper presents the results of a new experimental study on the pressure field generated by a rectangular nonaerated jet impinging on the bottom of a plunge pool, with reference to plunge pools confined by the presence of a drop structure at the upstream boundary. The mean dynamic pressure and fluctuating pressure components at the bottom of a plunge pool were measured and analyzed to define the features that are required in the evaluation of the stability of rock blocks in the plunge pool. The forces acting on blocks in the impingement region were computed, and from this, it was found that the effect of the mean dynamic pressure can be neglected compared with the effect of pressure fluctuations. Because the block stability depends only on the fluctuating pressure coefficient in the jet impingement region, this allows the use of experimental data reported in the literature to extend the range of applicability of this experimental study. This finding can be applied to any block shape. To highlight the application of the results, a design example is presented in this paper where the scale effect due to aeration is taken into account.